This may seem to be a stupid question, but the answer may help others with
your problem.
WHY do you need an alternate method to get the results of the Confidence()
function? I notice that you also had a question about calculating a MEAN
value?
Is the lack of a CONFIDENCE() function a problem with the language/Regional
setting for your copy of Excel or another problem? Do you not have the
Analysis ToolPak add-in available?